Affiliation: | (1) Department of Genetics, University of Alberta, T6G 2E9 Edmonton, Alberta, Canada;(2) Departamento de Biología Funcional, Area de Bioquimica, Facultad de Medicina, Universidad de Oviedo, E-33006 Oviedo, Spain;(3) Present address: Institut für Mikrobiologie, Heinrich-Heine-Universität Düsseldorf, Universitätsstrasse 1, W-4000 Düsseldorf 1, Federal Republic of Germany |